I wrote about this and included some videos here on beginner strumming habits: tips, posture, shoulder pain, etc:
http://dulcimer-noter-drone.blogspot.com/2010/01/video-tips-for-beginners-strumming.html
http://dulcimer-noter-drone.blogspot.com/2010/01/video-tips-for-beginners-strumming_08.html
Thank you, these were both very helpful and very clear!